Single-lens reflex digital cameras have been rapidly growing in popularity in recent years. With this single-lens reflex digital camera, when observing a subject using an optical viewfinder, the light (or the image of the subject) incident on an imaging optical system is reflected by a reflecting mirror arranged on the optical path, and guided to a viewfinder optical system. As a result, the subject image is converted into an erected image by a pentaprism and the like, and guided to the optical viewfinder. Therefore, a user can observe the subject image formed by the image optical system from the optical viewfinder.
On the other hand, when the imaging optical system is used for photographing, the reflecting mirror is retracted from the photographing optical path. As a result, the viewfinder optical path is switched to the photographing optical path, and the reflecting mirror returns to a fixed position immediately when photographing ends. This system is the same for a conventional silver halide camera or a digital camera, if it is a single-lens reflex system.
However, photographing using an optical viewfinder is extremely difficult for a beginner who is inexperienced with photographing using a digital camera.
Consequently, a camera system having a monitor photographing mode in which it is possible to observe a subject using a liquid crystal display monitor when photographing has been proposed (for example, refer to Patent Document 1).    Patent Document 1: Japanese published unexamined application JP2001-125173